This invention relates to an apparatus for indicating the status of sheets, and has particular application to an apparatus for indicating the status of currency notes.
In automatic currency note handling apparatus, such as cash dispensers or note counters, it is often necessary to detect the passage of multiple notes and to detect folds therein and any local attachments such as adhesive tape, staples or paper clips. In some applications, such as in a cash dispenser, it may be desired to count double notes as two notes and dispense them to a customer, while any notes having local attachments or folds are diverted to a reject bin as being in an unfit condition for dispensing to a customer. On the other hand, in other applications it may be desired to divert multiple notes into a reject bin but to permit notes having folds or local attachments to be passed through the apparatus for further handling. Thus, in order to optimize the operation of automatic currency note handling apparatus, it is desirable to identify not only the presence of an abnormality in note flow, but also to identify the particular type of abnormality so that proper action can be taken.
An apparatus for indicating the status of sheets and which is capable of distinguishing between different types of abnormalities, for example between a double sheet and a sheet carrying a local attachment, is known from European Patent Application No. 82306037.1 (Publication No. 0, 080, 309). An apparatus known from this European application includes a datum roller and a follower roller between which currency notes are fed in operation, the datum roller having a fixed axis and the axis of the follower roller being movable relative to that of the datum roller. The follower roller is biased towards the datum roller, and the ends of the follower roller are each supported by a pivotable bracket whereby the axis of the follower roller is tiltable relative to that of the datum roller. Two sensors are respectively arranged adjacent the ends of the follower roller. In response to a note passing through the nip of the rollers, each sensor produces a change in its output voltage, the magnitude of the change being dependent on the amount by which the corresponding end of the follower roller is displaced from the platen roller. The output voltages of the sensors are applied to an analyzing circuit whereby it is possible to determine an abnormality in the note flow such as a double note or a note having a fold or a local attachment. The sensors may be implemented by linear variable differential transformers.
The disadvantage of the known apparatus described above is that it may not be capable of distinguishing between a double currency note and a single note carrying a centrally positioned adhesive tape extending across the whole width of the note, as in the case of two halves of a torn note joined together by adhesive tape (which is a situation commonly encountered). Thus, if a note passing through the apparatus has such centrally positioned tape of thickness equal to that of the note, the two ends of the follower roller will be displaced from the datum roller by the same amount as would be the case if a double note were passing through the nip of the rollers.